The life modes and sizes of 98 species of higher crustaceans (Malacostraca) from Hornsund and Kongsfjorden (Svalbard fjords) were analyzed. The majority (90%) of the species were perennial, K strategists, with eight- to tenfold size differences between newborn and adult specimens. The largest species are carnivores and carrion feeders, while the smallest are sediment-dwelling suspension and deposit feeders. Compared with the crustacean fauna of northern Norway (over 500 species), the Svalbard fjord crustacean fauna is less diverse (below 150 species). The crustacean species populations from the Arctic fjord are more numerous (average number of ind./species/m2) compared to those of the northern Norway boreal fjords. Crustaceans with long life cycles and distinct size difference between juveniles and adults represent three to five ecologically different functional "species" each, since the smaller size groups of the same species differ with regard to theirmobility, food and habitat use. Thus, crustaceans are ecologically and functionally more diverse than expected from simple species count.
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